Neuromodulatory strategies targeting cortical and spinal pathways to facilitate paretic leg motor control during walking in individuals with stroke

Project Summary/Abstract This project aims to: (Aim 1) determine the effects of transcutaneous spinal cord stimulation (SCS) with constraint force to the non-paretic leg during treadmill walking on paretic leg motor control in individuals with stroke; and (Aim 2) determine the combined effects of transcutaneous SCS and non-invasive brain stimulation (NIBS) with constraint force to the non-paretic leg during treadmill walking on paretic leg motor control in individuals with stroke. After a stroke, individuals often rely on their non-paretic leg during walking, compensating for the impaired motor control and muscle weakness in the paretic leg. Current gait training approaches after stroke, such as treadmill training, have shown immediate benefits on walking function, yet more than 50% of stroke patients still struggle with impaired walking post-treatment. This persistent difficulty in walking may be attributed, at least in part, to the repetitive use of the compensatory strategies. Such strategies can further exacerbate the motor impairment of the paretic leg, contributing to greater gait asymmetry and higher risk of falls. Therefore, there is a critical need to develop gait interventions targeting paretic leg motor control during walking after stroke. Previously, we found that the application of constraint force to the non- paretic leg during treadmill walking facilitates the use of the paretic leg in individuals post-stroke. In this proposal, we aim to utilize non-invasive neuromodulatory approaches during this constraint force induced gait training to further enhance paretic leg motor control during walking post-stroke. Our preliminary results suggest that combining transcutaneous SCS with the application of constraint force to the non-paretic leg during treadmill walking facilitates greater step length, stance time, step height, muscle activity, and propulsive force of the paretic leg compared to constraint force induced gait training alone (Aim 1). We also propose that transcranial direct current stimulation (tDCS) combined with SCS during gait training may provide further improvements. One of the popular views into the mechanism of SCS is that stimulation increases excitability of the spinal circuits and modulates the responsiveness to corticospinal inputs. Given that individuals post-stroke demonstrate reduced descending cortical drive due to damaged corticospinal tract (CST), it is possible that the addition of tDCS, to upregulate the CST inputs, enhances the effectiveness of SCS which may further improve paretic leg motor control during walking. Results from this proposal may provide valuable insights to develop effective gait rehabilitation strategies to optimize walking recovery in individuals with stroke.